M81/M82 (2014/02/21)

It was an excellent night at Henry Coe, esp during the winter season. For the 1st time I took my STF8300C to the dark site, despite of a few software and hardware issues (you never know what problem is going to pop up) which had never happened before, I managed to capture some great subs.


Exposure: 16x600s
Data: 02/21/2014
Location: Henry Coe State Park, Morgan Hill, CA
Condition: Excellent seeing and transparency
Mount: CGEM
Imaging: AT111EDT + STF8300C
Guiding: AT72ED + SSAG
Software: Pixinsight

M42 – Orion Nebula (2014/12/23)

On Dec 23rd, the sky cleared up after the strongest storm in the past few years hit SF bay area, I setup my equipments at my backyard to test the new STF8300M with LRGB and narrow band filters.

4 images are posted here: RGB, LRGB, HaRGB and NarrowBand. All images are processed in Pixinsight with same flow, the detail of nebula is brought out using Pixinsight’s HDR and LHE toll. It should be noted that the difference between LRGB and RGB image is mainly due to post processing after combining LRGB, otherwise they look almost identical (probably because M42 is bright).

One issue I had was that somehow ACDNR did not work on stretched NB image (not sure why) so I had to use AT for final noise reduction.


M42 – RGB



M42 – LRGB



M42 – HaRGB



M42 -Narrow Band (OIII/SII/Ha)
LinearFit Ha to OIII and SII prior to combining


Exposure: L/R/G/B: 5x60s each; Ha/OIII/SII: 5x300s each. Bias/Dark/Flat calibrated

Location: My backyard in Sunnyvale CA

Condition: average seeing and transparency, heavy dew.

Mount: CGEM

Imaging: AT111EDT + STF8300M + FW8 + Baader LRGB/Ha/OIII/SII

Guiding: AT72ED + SSAG

Software: Pixinisight

M81, M82 and IFN (2015/01/24)

M81/M82 in Ursa Major is a popular target of astro imaging, however only some astrophotographers know “IFN”, and even fewer have imaged IFN surrounding M81/M82. I captured my first M81/M82 with STF8300C OSC CCD exactly one year ago, which is shown here. Back then I have never heard IFN, needless to say that I did not try to capture it (I dont think I could even if I did). Since then I have read some articles and seen a few images on internet about IFN, which made me wonder how easy/difficult to capture it with my slow telescope (F/7).  Since my new STF8300M should be more sensitive than STF8300C so I decided to give it a try.

It was a pleasant start at Henry Coe State Park, mild and calm weather, with excellent transparency and seeing, but wind started to pick up and seeing degraded drastically, so I had to stop taking Lum subs and switch to RGB. The winds subsidized ~4AM and seeing improved, though not as good as the beginning. I was able to take ~90min Lum and 60min RGB each.

I was not very confident whether 6 Lum subs were sufficient (my plan was 12 subs). After getting home I loaded Lum subs to Pixinsight, to my surprise I was able to see the hint of IFN without much processing.

The following two images are the final results, they are processed the same except that one is stretched with Masked Stretch, and the other with Histogram Transformation. As expected, Masked Stretch gives better color saturation. (however I have to use HT stretched L since HDRWaveletTransformation does not work well on MT stretched L, not sure why because it does work on MT stretched RGB).

In both images, IFN is clearly visible, esp in the region below M82, above M81, and below right tip of M81. It should be noted that due to light pollution, there was severe background gradient in RGB image, so the color of IFN on top left corner is probably the residual color of back ground extraction. The color of IFN below M81 and M82 should be more neutral though I am not completely sure.

There are two major challenges when processing the image:
– The background gradient of RGB image. The gradient is pretty bad due to light pollution from silicon valley, Pixinsight DBE tool removes majority of gradient but there is still some residual visible.
– Background noise reduction to bring out faint IFN. I find for this image (also many images with large portion of background), TGV tends to amplify the large scale background noise in linear image which is difficult to manage after stretch. It is more efficient to use AT for linear noise reduction and ACDNR for back ground noise reduction after stretch.


M81/M82 (Using Pixinsight MaskedStretch)


M81/M82 (Using Pixisight HistogramTansformation)

On 2/23, I took 8 Ha subs and re-processed the image. There is slight more blue tint on the back ground than the original image.


M81/M82 (with Ha)


Date: 01/24/2015

Location: Henry Coe State Park, Morgan Hill, CA

Condition: excellent transparency, excellent to poor seeing, calm to breezy

Date: 02/23/2015

Location: MonteBello OSP, CA

Condition: excellent transparency, below average seeing, breezy, dry

Equipment: AT111EDT on CGEM, guided by SSAG+AT72ED. STF8300M+FW8+Baader LRGB

Exposure: L – 6x900s, R – 12x300s Bin2x2, G – 12x300s Bin2x2, B – 11x300s Bin2x2. Ha – 8x900s Bin1x1 (2/23/2015), Dark/Bias/Flat calibrated

Software: Pixinsight